A method for objective assessment of disease activity in Inflammatory Bowel Disease (IBD) might facilitate the management of patients as well as the evaluation of therapeutic trials. Over the years, several different clinical and laboratory indices including radioactive scanning techniques have been used to determine disease activity in IBD (1-13). The labelling of leucocytes with the radioactive isotopes .sup.111 Indium and .sup.99 Technetium has given promising results, and fectal excretion of these isotopes has been regarded as the "gold standard" of disease activity in IBD (14-15). Despite their high sensitivity and specificity, these techniques have limitations; they are cumbersome, costly, and expose the patient, especially the liver and spleen, to radiation (11, 16, 17, 18, 19). For these reasons the use of isotope techniques are not recommended in children, adolescence and fertile women (13, 21).